A longstanding objective within the materials, engineering, biomedical and analytical sciences has been the design of ever-smaller structures and devices for use in miniaturize systems capable of performing specific functions, such as sensors, transducers, signal processors or computers. Of particular interest as potential building blocks in this context have been functional materials having predetermined properties. Patterned films composed of suitable polymers and polymer-microparticle composite films offer particularly attractive opportunities to realize hierarchically organized structures of functional materials and to provide confinement and segregation for performing “local” chemical reactions.
Several methods of preparing patterned polymer films and polymer-microparticle composite films have been described. In one example, polymer molding has been used to prepare polymeric films. Beginning with a master that is fabricated from a silicon (Si) wafer using conventional lithographic techniques, a mold is made using an elastomer such as polydimethylsiloxane (PDMS). The mold is then used to produce replicas in a UV-curable polymer such as polyurethane. The applicability of this technique of polymer molding, long used for replication of micron-sized structures in devices such as diffraction gratings, compact disks, etc., recently has been extended to nanoscale replication (Xia, Y. et al., Adv. Mater. 9: 147 (1997), Jackman, R. J. et al., Langmuir. 15:2973 (1999), Kim, E. et al. Nature 376, 581 (1999).
Photolithography has been used to produce patterned, stimuli-sensitive polymeric films which can be further functionalized with bioactive molecules and which undergo abrupt changes in volume in response to changes in pH and temperature (Chen, G. et al., Langmuir. 14:6610 (1998); Ito, Y. et al., Langmuir 13: 2756 (1997)). UV-induced patterned polymerization of various hydrogel structures within microchannels has been described as a means for the autonomous control of local flow (Beebe, D. J. et al., Nature. 404:588 (2000)).
Surface-initiated ring-opening metathesis polymerization following microcontact printing has been used to create patterned polymer layers which remain attached to the surface and produce structures of controlled vertical and lateral dimensions (Jeon, N. L. et al., Appl. Phys. Lett. 75:4201 (1999)). Other techniques such as thermal radical polymerization (Liang, L., J. Appl. Polym. Sci. 72:1, (1999)) and UV-induced polymerization (Liang, L., J. Membr. Sci. 162:235 (1999)) have been used to generate surface confined thin, uniform and stimuli-sensitive polymeric films.
Sarasola, J. M. et al. (J. Electroanal. Chem. 256:433, (1988) and Otero, T. F. et al., J. Electroanal. Chem. 304:153, (1991) describe electropolymerization of acrylamide gels using Faradaic process. Acrylaminde gels are prepared on electrode surfaces by an anodic oxidative polymerization process using the electroactive nature of acrylamide monomers.
Polymerization of crosslinked acrylamide has been described to produce a matrix of glass-immobilized polyacrylamide pads which were activated with receptor molecules of interest including oligonucleotides or proteins. The use of the resulting porous and highly hydrated matrix for simultaneous monitoring of ligand-receptor binding reactions has been reported (Proudnikov, D. et al., Anal. Biochem. 259:34 (1998); Yershov, G., Proc. Natl. Acad. Sci. U.S.A. 93:4913 (1996), LaForge, S. K., Am. J. Med. Genet. 96:604 (2000); Khrapko, K. R. et al. U.S. Pat. No. 5,552,270, 1996; Ershov, G. M. et al. U.S. Pat. No. 5,770,721, 1998; Mirzabekov et al. U.S. Pat. No. 6,143,499.).
A process for the assembly of a 3-D array of particles has been described which is based on the synthesis of a core-shell latex particle containing a core polymer with a glass transition temperature significantly higher than that of the shell polymer. In accordance with that process, particles were assembled into a 3-D close packed structure and annealed in such a way that the core particle remained unaltered while the shell polymer flowed, resulting in a continuous matrix embedding an organized 3-D array of core particles (Kalinina, 0. and Kumacheva, E., Macromolecules. 32:4122 (1999); Kumacheva, E. et al., Adv. Mater. 11:231 (1999), Kumacheva, E. et al., U.S. Pat. No. 5,592,131 (1999)).
The encapsulation of a colloidal crystalline array within a thin, environmentally sensitive hydrogel matrix capable of swelling in response to changes in pH and temperature has been described. In other instances, the hydrogel contained immobilized moieties capable of triggering the swelling of the gel in the presence of particular analytes. The swelling of the gel matrix increases the periodicity of the colloidal crystal array and produces a shift in Bragg diffraction peaks in the spectra of the scattered light(Holtz, J. H. et al., Anal. Chem. 70:780 (1998); Haacke, G. et al., U.S. Pat. No. 5,266,238, 1993; Asher, S. A., U.S. Pat. No. 5,281,370, 1994). The process of forming the colloid crystal relies on passive diffusive transport of particles within the prepolymer reactive mixture.
Each of the aforementioned references are incorporated herein by reference in its entirety.